1. Field of the Invention
The present invention relates to a developer waste liquid regenerating apparatus and method.
2. Related Background Art
In recent years, manufacture of electronic parts such as semiconductors, liquid crystals, printed boards and the like has been accomplished by a manufacturing process involving formation of a negative or positive photoresist film on a substrate such as an Si wafer as the film-forming step, irradiation of light or the like through a pattern mask as the irradiation step, using a developer liquid to dissolve unwanted photoresist as the developing step, etching treatment as the etching step and removal of the insoluble photoresist film from the substrate as the stripping step.
The developer liquid used for the developing step is usually tetraalkylammonium hydroxide (hereinafter referred to as “TAAH”). Developer waste liquids discharged from developing steps therefore contain dissolved photoresist and TAAH.
One method of treating developer waste liquids is the method for pretreatment and regeneration of TAAH-containing waste liquids disclosed in Japanese Unexamined Patent Publication HEI No. 11-262765. In the method for pretreatment and regeneration of TAAH-containing waste liquids described in this publication, the TAAH-containing waste liquid is neutralized in a suitable acid to precipitate the photoresist in the waste liquid. The TAAH-containing waste liquid is then introduced into a membrane separator to separate and remove the solid portion (consisting mainly of photoresist). The TAAH-containing liquid from which the solid portion has been removed by the membrane separator is concentrated using an evaporator for concentration and volume reduction of the TAAH-containing liquid.
This solid-free and neutralized TAAH-containing liquid is then regenerated by electrodialysis. Purified water or fresh TAAH is added to the obtained concentrated TAAH liquid to adjust the concentration for reutilization as a developer liquid for electronic parts.
Also, Japanese Unexamined Patent Publication HEI No. 11-192481 discloses a technique wherein a nanofiltration membrane is used for membrane separation of the photoresist developer waste liquid to obtain a concentrate containing impurities such as mainly the photoresist and a permeating liquid containing mainly tetraalkylammonium ion.